Arnaud,
I think you are asking about surface energy rather than surface tension. 
We use the readily available Dyne Pens which have solutions calibrated 
back to an ASTM standard.

I generally use this rule of thumb regardless of the coating used.

Under 30 dynes/cm:  Coating adhesion will be poor
30-35 dynes/cm:  Coating adhesion will be slightly better, but you can 
expect more frequent cases of delamination.
35-40 dynes/cm:  Coating adhesion generally good, but can have some 
periodic delamination or adhesion issues.
40-45 dynes/cm:  Coating adhesion is good and only rarely will you see 
delamination problems
45+ dynes.cm:  Good adhesion.

Of course, there will always be special cases but this is a good starting 
point.

Doug Pauls



From:   GRIVON Arnaud <[log in to unmask]>
To:     <[log in to unmask]>
Date:   02/03/2014 10:48 AM
Subject:        [TN] [COM] Solder Mask Surface Tension for Conformal 
Coating Adhesion
Sent by:        TechNet <[log in to unmask]>



Hello TechNet,

I would like to sense the best practices in terms of solder mask surface 
tension with respect to conformal coating adhesion :

-          Which standard/test method are you using?

-          Which requirement (e.g. minimum value in dyn/cm²) would you 
accept for the various CC types (acrylics, urethanes, silicone, parylene)?
Thanks in advance for the insights.
Best regards,

Arnaud Grivon


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________



______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________